Investigation and optimal design of partially encapsulated metal foam in a latent heat storage unit for buildings

Metal foam (MF) is considered an effective method to enhance thermal conductivity and uniformity of latent heat thermal energy storage (LHTES). However, the insertion of MF will reduce the effective volume of phase change material (PCM), leading to lower energy storage capacity and higher energy storage costs. To solve this problem, this study prepared MF/stearic acid (SA) composite phase change materials (CPCM), established a visual experimental platform and developed a validated local thermal non-equilibrium (LTNE) model. Numerical investigated the influence of “Taguchi-configuration”, “Right half-configuration”, and “L-configuration” MF partially filling strategies on the heat transfer characteristics of LHTES unit, aiming to synergistically utilize the buoyancy convection of molten PCM and the thermal conductive penetration of MF. Further considering the influence of the ratio (ξ) of height to width of the natural convection area on the melting characteristics in the LHTES unit. The melting rate, temperature distribution, and energy storage density were examined and analyzed in detail. Results show that “L-configuration” filling outperformed “Right half-configuration”, and “Taguchi-configuration”. It is indicated that partially filling MF with 50 % achieves a more significant acceleration of the PCM melting rate compared to 100 % MF filling. Contributing a 7.1 % increase in thermal storage rate density and a 50 % reduction in cost. Compared with literature's partially filling strategies, the proposed filling strategy in this study exhibited better advantages, with a potential enhancement of the melting rate by 11.25 % under identic conditions. As the ratio of height to width of the natural convection area decreased, the natural convection buoyancy increased. Correspondingly, the thermal storage rate density increased with the decrease of the ratio. Partially filling designs provide a competitive solution for building energy-saving applications by increasing energy storage efficiency and reducing costs.